The 25L6GT is a cousin of the very popular 6L6. It is designed for use in single ended audio stages within a 300 mA heater chain environment. As a single ended audio amplifier it can produce 4.3 Watts.

The wide glass envelope is 27 mm in diameter and, excluding the IO base pins, is 68 mm tall.

References: Datasheet, ¹⁰⁴⁰ & ¹⁰⁴³. Type 25L6GT was first introduced^¶ in 1937.

 
Pin Connections

IO	1	2	3	4	5	6	7	8
	m	h	a	g2	g1	-	h	k

 
Absolute Maximum Operating Conditions^¶

Beam Tetrode	Vh	Ah	Va	Vs	Vg	mAa	mAs	ra	gm	Pout	D
	25	0.3	200	110	-8	50	2	30,000	9.5	4.3W	10%

Thanks to Frank Philipse for supplying the above PDF datasheet